The present invention relates generally to brakes for motor vehicles, and more particularly to an electric caliper for a brake system in a motor vehicle.
A brake system for a motor vehicle, and in particular an automotive vehicle, functionally reduces the speed of the vehicle or maintains the vehicle in a rest position. Various types of brake systems are commonly used in automotive vehicles, including hydraulic, anti-lock or xe2x80x9cABS,xe2x80x9d and electric or xe2x80x9cbrake by wire.xe2x80x9d For example, in a hydraulic brake system, the hydraulic fluid transfers energy from a brake pedal to a brake pad for slowing down or stopping rotation of a wheel of the vehicle. Electronics control the hydraulic fluid in the hydraulic brake system. In the electric brake system, the hydraulic fluid is eliminated. Instead, the application and release of the brake pad is controlled by an electric caliper.
Traditionally, hydraulic fluid is a very efficient means of transferring a load, since a brake system in an automotive vehicle must be able to transfer a load of about fourteen thousand (14,000) pounds. An electric brake system accomplishes this load transfer through the electric caliper. Generally, the electric caliper includes a motor and a gear system. Typically, either a few large gears or many small gears for the gear system are needed to achieve the necessary load transfer. Also, the geometry of the motor influences its efficiency, since the preferred shape is long and thin. However, there is a limited amount of space available in the wheel for packaging the type of gears or motor necessary to obtain the same load transfer as in the hydraulic brake system. Therefore, space limitations constrain the use of an electric caliper in an automotive vehicle.
The present invention is a ball screw assembly for a motor vehicle electric caliper. The ball screw assembly comprises a ball screw, a carrier, and a ball screw nut. The ball screw has at least one internal groove, and the carrier has at least one projection engaging the at least one groove. The ball screw nut operatively engages the ball screw.
Accordingly, it is an object of the present invention to provide an electric caliper for a brake system that can be packaged within the available space of a wheel.
Another object of the present invention is to provide an electric caliper including a ball screw.
Still another object of the present invention is to provide an electric caliper of the type described above that has a ball screw positioned around a motor which effectively increases gear reduction capability of the ball screw.
Still another object of the present invention is to provide an electric caliper of the type described above which reduces the number of parts found in prior art electric calipers, and reduces the cost of manufacturing the remaining parts.
Still another object of the present invention is to provide a ball screw assembly of the type described above which has a ball screw with internal splines or keyways.
These and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.